Bedside Spirometry for Acute Lung Injury

The diagnosis of Acute Respiratory Distress Syndrome (ARDS) is a syndromic diagnosis that groups together patients who may have very different prognoses and respond differently to the same therapies. Additionally, non-invasive ventilation (NIV) has shown highly contrasting results in the early management of ARDS. One of the predictive criteria for NIV failure is an excessively high tidal volume during non-invasive ventilation. SPIRALI is a pilot study evaluating the relevance of a respiratory physiology parameter, the tidal volume relative to the theoretical ideal body weigh, in the phenotypic classification of non-intubated ARDS patients. In this initial approach, the investigators will compare the tidal volume during high-flow oxygen therapy with the tidal volume obtained under NIV (after applying a settings optimization algorithm). The investigators hypothesize that if tidal volume is linked to each situation, the same patients will exhibit a high tidal volume both during spontaneous ventilation and under NIV.